Kazuhisa Morimoto

J-aggregation of photochromic spiropyran in Langmuir-Blodgett films

Abstract The possibility of controlling the photochromic reactions of two different spiropyrans was investigated using the Langmuir-Blodgett technique. The spiropyran having a long chain formed an unstable monolayer without UV light and a stable monolayer with UV light. The spiropyran having two long chains, however, could form more stable monolayers with and without irradiation and the most stable monolayer was formed on mixing with n-octadecane in a molar ratio of 1:2. The assemblies of this monolayer, under UV irradiation at temperatures above 35 °C, exhibited a sharp and intense band at a longer wavelength, which could be assigned to the formation of J-aggregates. The half-decay period in the dark was 104 times longer than that of conventional spiropyrans. The possibilities of three-dimensional high density optical memory with this photochromic spiropyran are suggested.

Controls of photochromic reactions in spiropyran Langmuir-Blodgett films☆

The possibility of controlling photochromic reactions has been investigated in Langmuir-Blodgett (LB) films. The formation of J aggregates of a spiropyran (SP1822) with two long chains has been found previously. We have studied another possibility using LB films of 1′-octadecyl-3′,3′-dimethyl-6-nitro-8-methoxy- spiro[2H-1-benzopyran-2,2′-indoline] (SP1801). SP1801 at the air-water interface gave a monolayer which showed the photomerocyanine form. The LB film of the compound returned to the spiropyran form in the dark. The LB film of the hetero structure with SP1801 and stearic acid, however, turned to J aggregates from the photomerocyanine form spontaneously in the dark. The absorption of the J aggregates was a sharp and intense band, and the half-decay period in the dark was 104 times longer than that of conventional spiropyrans. SP1801, in addition to SP1822, is suggested as a candidate for a multifrequency optical memory system with several J-aggregated photochromic compounds having different sharp absorption bands.

Frictional properties of monomolecular layers of silane compounds

The frictional performance of ultrathin films was evaluated, especially in monomolecular layers of silane compounds. The monolayer of γ-(N,N- dioctadecylsuccinylamino)propyltriethoxysilane is one of the candidates for the best lubricating film. The film exhibited a low coefficient of kinetic friction, μk < 0.1, and 105 transits without stick-slip. From X-ray photoelectron spectroscopy and Fourier transform IR analysis, both the adhesion between the molecules of the lubricant and the surface of the substrate and the cohesion between the molecules of the lubricant are extremely strong.

Molecular arrangements of photochromic spiropyrans on a subphase

Abstract The photochromic behaviours of long alkyl chain spiropyrans were observed in a monomolecular layer at the air-water interface. UV-induced merocyanines of SP16 and SP1822 formed J aggregates on the subphase, whereas that of SP1801 did not form. They exhibited different molecular arrangements in the photochromic reaction processes, including the formation of J aggregates. Models of the molecular arrangements of these compounds on the subphase are presented.

Pitch and Sense of Helix in Mixtures of Optically Active Azo or Azoxy Compounds and Nematic Liquid Crystal

Mixtures of azo or azoxy compound with asymmetric side chains and a nematic liquid crystal, and the pitch and sense of the helix were examined. Compounds with two identical optically active side chains exhibited the twisting power twice that of compounds with one optically active side chain. As a result, it was found that a feature value (M/Pc), where M, P and c are molecular weight, pitch and concentration by weight, is inherent to an optically active side chain and that the value is additive for compounds with two optically active side chains.

Preparation and properties of optical notch filters of cholesteric liquid crystals

Abstract We investigated the influence of preparative conditions of cholesteric-liquid-crystal (CLC) solid films on their cholesteric structures. They are made of poly[γ-butyl- l (or d )-glutamate] (PBuL(D)G and triethylene glycol dimethacrylate (TGDM), and have the ability to reflect the light in a specified wavelength region. When these films were combined with conventional colour filters, the colour reproduction region was enlarged by about 25% in the area of the CIE chromaticity diagram.

Dye Sensitization of Photoconductivity of Poly-N-Vinylcarbazole. I. Quantum Yield

The photocurrent of the dye-sensitized poly-N-vinylcarbazole (PNVC) film was measured. The dyes were used carbonium salts, benzopyrylium salts and crystal violet. These dyes were found to enhance the photocarriers in the film both at the first excitation band of PNVC and at the excitation band of the dyes. Since photocarriers were observed to be holes, it is concluded that the electron transfer occurs from PNVC to dyes with the absorption of photons and that the quantum yield of photocarriers is related to the rate of this electron transfer. The quantum yield was deduced from the combination of the photocurrent and the decay rate of the surface charge and was found to be more than 10-1 for the excitation of PNVC and 10-2~10-1 for the dye-excitation.

Organic photoconductive layers sensitized with triarylcarbonium salts.

The electrophotographic layer consisting of poly-3,6-dibromo-N-vinylcarbazole was sensitized with twenty-seven kinds of triarylcarbonium salts. The carbonium salt compounds used have the formula: [equation] The novel sensitizers differ in two points from the well-known triphenylmethane dyestuffs sensitizers for the organic electrophotoconductors. First, the triphenylmethane dyestuffs have at least two radicals such as amino or dimethylamino radical. The novel sensitizers have not such a radical. Second, the novel sensitizers have an extreme ability to increase the photosensitivity of organic photoconductors. When the photoconductive polymer sensitized with carbonium salts is applied to semitransparent paper, cellophane papers or plastic sheet, a transparent electrophotographic material can be obtained. These materials are superior to sensitized zinc oxide paper in photosensitivity. Such a transparent material can be used as a master for diazo copy, for overhead projection copy, or for slides.

Dye Sensitization of Photoconductivity of Poly-N-Vinylcarbazole II. Fluorescence Quenching and Charge Transfer

Fluorescence and excitation spectra of poly-N-vinylcarbazole (PNVC) and dyes were measured. The fluorescence of dyes decreased with the addition of PNVC and that of PNVC also decreased with the addition of dyes, with a peak at about 425 mµ. The quenching of PNVC fluorescence was found to be more remarkable for dyes having larger sensitization effects on the photocurrent in PNVC films. These results suggest that both the fluorescence quenching and the sensitization of the photocurrent are due to the electron transfer from PNVC to dyes under illumination.

Infrared Absorption Spectra of Acylhydrazone Derivatives

X-CO-NH-N=CH-Y骨格をもつ10種類のアシルヒドラゾン誘導体の赤外吸収スペクトルを臭化カリウム錠剤法により岩塩領域において測定した。これらのスペクトルを比較し,また類似物質から得られた振動数と比較検討することにより,つぎのように吸収帯の帰属を行なった。1650cm-1付近;アミド1吸収帯,1600cm-1付近;ベンゼン核面内骨格および>C=N-伸縮,1525cm-1付近;アミドII吸収帯,1500cm-1付近;ベンゼン核面内骨格,1435cm-1付近;-CH3逆対称変角,1368cm-1付近;-CH3対称変角,1290cm-1付近;アミド醗吸収帯,1184,1170cm-1付近;-N(CH3)2骨格,1230,1060,946cm-1付近;4-ジメチルアミノフェニレン基,818cm-1付近;同基のベンゼン核のCH面外変角。